In a machine tool on which an NC unit (numerical control unit) is mounted, a work is machined into a desired product shape by executing the NC program. To create the NC creation program for creating the NC machining program, recently, an automatic programming technique using a microcomputer referred to as an automatic, programming device has been frequently used.
The early automatic programming devices were not connected to the CAD data, and hence, it was necessary to perform programming, while watching the machining shape in a drawing or the like. However, recently, some techniques relating to the automatic programming device that creates the NC machining program by the CAD data have been proposed.
For example, in Patent Literature 1 (Japanese Patent Application Laid-Open No. 2002-189510), feature data of a machined product is extracted from the CAD data to set a machining process and a machining area for each machining process, material data and a machining model for each machining process are created, the created machining process data and machining model data are stored, tool path data is created based on the machining process data, material data, machining model data, tool data, and cutting condition data, to create virtual work shape data after completing the respective processes, as well as creating fabrication information based on the created process data, material data, tool path data, and virtual work shape data.
In Patent Literature 2 (Japanese Patent Application Laid-Open No. 2002-268718), when a machining path for machining a workpiece based on a three-dimensional CAD data of a part is created, machining information for all portions to be machined in a shape indicated by the three-dimensional CAD data is extracted, the extracted machining information is edited to determine a machining process, and the machining path is created based on the determined machining process.
In the automatic programming device, it is necessary to divide a machining area, which is a difference between a work model and a product model, into a first process in which one end of the work model is held to perform machining, and a second process in which the other end of the work model is held to perform machining.
Patent document 3 (Japanese Patent Application Laid-Open No. H2-62603) discloses a numerical control unit that controls a two-spindle machine tool having two spindles, that is, a main spindle and a sub-spindle, wherein an operator instructs a temporary dividing position between the first process and the second process via an input unit in the state that a machining shape is displayed on a display unit, thereby instructing the temporary dividing position on an outer diameter side and an inner diameter side of the work.
However, the conventional process-dividing processing is only for manually setting the process-dividing position by the operator, and hence, time for the manual setting by the operator is required, thereby impeding efficient programming.
The present invention has been achieved to solve the above problems, and it is therefore an object of the invention to provide an automatic programming method and device that can automatically perform process division and perform efficient programming operations.